[ELF/tests] Use cpio -it instead of cpio -t.

OpenBSD's cpio does not accept the -t option without -i.
Apparently some systems implement cpio -t as a shortcut
for cpio -it, the latter is the only thing that's documented.
This change avoids test failures on OpenBSD.

Patch by Mark Kettenis!

Differential Revision:  https://reviews.llvm.org/D28002

llvm-svn: 290252